DataSource.Factory

Factory for DataSources.

Data-loading systems of an application or library can implement this interface to allow LiveData<PagedList>s to be created. For example, Room can provide a DataSource.Factory for a given SQL query:

@Dao
interface UserDao {
    @Query("SELECT * FROM user ORDER BY lastName ASC")
    public abstract DataSource.Factory<Integer, User> usersByLastName();
}

In the above sample, Integer is used because it is the Key type of PositionalDataSource. Currently, Room uses the LIMIT/OFFSET SQL keywords to page a large query with a PositionalDataSource.

Parameters
<Key : Any>

Key identifying items in DataSource.
<Value : Any>

Type of items in the list loaded by the DataSources.

Summary

Public constructors
<Key : Any, Value : Any> Factory()
android

Public functions
() -> PagingSource<Key, Value>
android
abstract DataSource<Key, Value>

Create a DataSource.
android
open DataSource.Factory<Key, ToValue>
<ToValue : Any> map(function: Function<Value, ToValue>)

Applies the given function to each value emitted by DataSources produced by this Factory.
android
open DataSource.Factory<Key, ToValue>
<ToValue : Any> map(function: (Value) -> ToValue)

Applies the given function to each value emitted by DataSources produced by this Factory.
android
open DataSource.Factory<Key, ToValue>
<ToValue : Any> mapByPage(function: Function<List<Value>, List<ToValue>>)

Applies the given function to each value emitted by DataSources produced by this Factory.
android
open DataSource.Factory<Key, ToValue>
<ToValue : Any> mapByPage(function: (List<Value>) -> List<ToValue>)

Applies the given function to each value emitted by DataSources produced by this Factory.
android

Extension functions
LiveData<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toLiveData(
    config: PagedList.Config,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchExecutor: Executor
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android
LiveData<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toLiveData(
    pageSize: Int,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchExecutor: Executor
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android
Flowable<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toFlowable(
    config: PagedList.Config,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchScheduler: Scheduler?,
    notifyScheduler: Scheduler?,
    backpressureStrategy: BackpressureStrategy
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android
Flowable<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toFlowable(
    config: PagedList.Config,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchScheduler: Scheduler?,
    notifyScheduler: Scheduler?,
    backpressureStrategy: BackpressureStrategy
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android
Flowable<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toFlowable(
    pageSize: Int,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchScheduler: Scheduler?,
    notifyScheduler: Scheduler?,
    backpressureStrategy: BackpressureStrategy
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android
Flowable<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toFlowable(
    pageSize: Int,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchScheduler: Scheduler?,
    notifyScheduler: Scheduler?,
    backpressureStrategy: BackpressureStrategy
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android
Observable<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toObservable(
    config: PagedList.Config,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchScheduler: Scheduler?,
    notifyScheduler: Scheduler?
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android
Observable<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toObservable(
    config: PagedList.Config,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchScheduler: Scheduler?,
    notifyScheduler: Scheduler?
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android
Observable<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toObservable(
    pageSize: Int,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchScheduler: Scheduler?,
    notifyScheduler: Scheduler?
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android
Observable<PagedList<Value>>
<Key : Any, Value : Any> DataSource.Factory<Key, Value>.toObservable(
    pageSize: Int,
    initialLoadKey: Key?,
    boundaryCallback: PagedList.BoundaryCallback<Value>?,
    fetchScheduler: Scheduler?,
    notifyScheduler: Scheduler?
)

This function is deprecated. PagedList is deprecated and has been replaced by PagingData
android

Public constructors

Factory

android 
<Key : Any, Value : Any> Factory()
Parameters
<Key : Any>

Key identifying items in DataSource.
<Value : Any>

Type of items in the list loaded by the DataSources.

Public functions

asPagingSourceFactory

android
Added in 3.0.0
fun asPagingSourceFactory(
    fetchDispatcher: CoroutineDispatcher = Dispatchers.IO
): () -> PagingSource<Key, Value>

create

android
Added in 2.0.0
abstract fun create(): DataSource<Key, Value>

Create a DataSource.

The DataSource should invalidate itself if the snapshot is no longer valid. If a DataSource becomes invalid, the only way to query more data is to create a new DataSource from the Factory.

androidx.paging.LivePagedListBuilder for example will construct a new PagedList and DataSource when the current DataSource is invalidated, and pass the new PagedList through the LiveData<PagedList> to observers.

Returns
DataSource<Key, Value>

the new DataSource.

map

android
Added in 2.0.0
open fun <ToValue : Any> map(function: Function<Value, ToValue>): DataSource.Factory<Key, ToValue>

Applies the given function to each value emitted by DataSources produced by this Factory.

Same as mapByPage, but operates on individual items.

Parameters
<ToValue : Any>

Type of items produced by the new DataSource, from the passed function.
function: Function<Value, ToValue>

Function that runs on each loaded item, returning items of a potentially new type.
Returns
DataSource.Factory<Key, ToValue>

A new DataSource.Factory, which transforms items using the given function.
See also
mapByPage
map
mapByPage

map

android
Added in 3.1.0
open fun <ToValue : Any> map(function: (Value) -> ToValue): DataSource.Factory<Key, ToValue>

Applies the given function to each value emitted by DataSources produced by this Factory.

An overload of map that accepts a kotlin function type.

Same as mapByPage, but operates on individual items.

Parameters
<ToValue : Any>

Type of items produced by the new DataSource, from the passed function.
function: (Value) -> ToValue

Function that runs on each loaded item, returning items of a potentially new type.
Returns
DataSource.Factory<Key, ToValue>

A new DataSource.Factory, which transforms items using the given function.
See also
mapByPage
map
mapByPage

mapByPage

android
Added in 2.0.0
open fun <ToValue : Any> mapByPage(function: Function<List<Value>, List<ToValue>>): DataSource.Factory<Key, ToValue>

Applies the given function to each value emitted by DataSources produced by this Factory.

Same as map, but allows for batch conversions.

Parameters
<ToValue : Any>

Type of items produced by the new DataSource, from the passed function.
function: Function<List<Value>, List<ToValue>>

Function that runs on each loaded page, returning items of a potentially new type.
Returns
DataSource.Factory<Key, ToValue>

A new DataSource.Factory, which transforms items using the given function.
See also
map
map
mapByPage

mapByPage

android 
open fun <ToValue : Any> mapByPage(function: (List<Value>) -> List<ToValue>): DataSource.Factory<Key, ToValue>

Applies the given function to each value emitted by DataSources produced by this Factory.

An overload of mapByPage that accepts a kotlin function type.

Same as map, but allows for batch conversions.

Parameters
<ToValue : Any>

Type of items produced by the new DataSource, from the passed function.
function: (List<Value>) -> List<ToValue>

Function that runs on each loaded page, returning items of a potentially new type.
Returns
DataSource.Factory<Key, ToValue>

A new DataSource.Factory, which transforms items using the given function.
See also
map
map
mapByPage

Extension functions

toLiveData

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toLiveData(
    config: PagedList.Config,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchExecutor: Executor = ArchTaskExecutor.getIOThreadExecutor()
): LiveData<PagedList<Value>>

Constructs a LiveData<PagedList>, from this DataSource.Factory, convenience for LivePagedListBuilder.

No work (such as loading) is done immediately, the creation of the first PagedList is deferred until the LiveData is observed.

Parameters
config: PagedList.Config

Paging configuration.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / PagingSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchExecutor: Executor = ArchTaskExecutor.getIOThreadExecutor()

Executor for fetching data from PagingSources.
See also
LivePagedListBuilder

toLiveData

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toLiveData(
    pageSize: Int,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchExecutor: Executor = ArchTaskExecutor.getIOThreadExecutor()
): LiveData<PagedList<Value>>

Constructs a LiveData<PagedList>, from this DataSource.Factory, convenience for LivePagedListBuilder.

No work (such as loading) is done immediately, the creation of the first PagedList is deferred until the LiveData is observed.

Parameters
pageSize: Int

Page size.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / PagingSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchExecutor: Executor = ArchTaskExecutor.getIOThreadExecutor()

Executor for fetching data from DataSources.
See also
LivePagedListBuilder

toFlowable

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toFlowable(
    config: PagedList.Config,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchScheduler: Scheduler? = null,
    notifyScheduler: Scheduler? = null,
    backpressureStrategy: BackpressureStrategy = BackpressureStrategy.LATEST
): Flowable<PagedList<Value>>

Constructs a Flowable<PagedList>, from this DataSource.Factory, convenience for RxPagedListBuilder.

The returned Flowable will already be subscribed on the fetchScheduler, and will perform all loading on that scheduler. It will already be observed on notifyScheduler, and will dispatch new PagedLists, as well as their updates to that scheduler.

Parameters
config: PagedList.Config

Paging configuration.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / DataSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchScheduler: Scheduler? = null

Scheduler used to fetch from DataSources, generally a background thread pool for e.g. I/O or network loading.
notifyScheduler: Scheduler? = null

Scheduler that receives PagedList updates, and where PagedList.Callback calls are dispatched. Generally, this is the UI / main thread.
backpressureStrategy: BackpressureStrategy = BackpressureStrategy.LATEST

BackpressureStrategy for the Flowable to use.
See also
RxPagedListBuilder
toObservable

toFlowable

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toFlowable(
    config: PagedList.Config,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchScheduler: Scheduler? = null,
    notifyScheduler: Scheduler? = null,
    backpressureStrategy: BackpressureStrategy = BackpressureStrategy.LATEST
): Flowable<PagedList<Value>>

Constructs a Flowable<PagedList>, from this DataSource.Factory, convenience for RxPagedListBuilder.

The returned Flowable will already be subscribed on the fetchScheduler, and will perform all loading on that scheduler. It will already be observed on notifyScheduler, and will dispatch new PagedLists, as well as their updates to that scheduler.

Parameters
config: PagedList.Config

Paging configuration.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / DataSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchScheduler: Scheduler? = null

Scheduler used to fetch from DataSources, generally a background thread pool for e.g. I/O or network loading.
notifyScheduler: Scheduler? = null

Scheduler that receives PagedList updates, and where PagedList.Callback calls are dispatched. Generally, this is the UI / main thread.
backpressureStrategy: BackpressureStrategy = BackpressureStrategy.LATEST

BackpressureStrategy for the Flowable to use.
See also
RxPagedListBuilder
toObservable

toFlowable

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toFlowable(
    pageSize: Int,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchScheduler: Scheduler? = null,
    notifyScheduler: Scheduler? = null,
    backpressureStrategy: BackpressureStrategy = BackpressureStrategy.LATEST
): Flowable<PagedList<Value>>

Constructs a Flowable<PagedList>, from this DataSource.Factory, convenience for RxPagedListBuilder.

The returned Flowable will already be subscribed on the fetchScheduler, and will perform all loading on that scheduler. It will already be observed on notifyScheduler, and will dispatch new PagedLists, as well as their updates to that scheduler.

Parameters
pageSize: Int

Page size.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / DataSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchScheduler: Scheduler? = null

Scheduler used to fetch from DataSources, generally a background thread pool for e.g. I/O or network loading.
notifyScheduler: Scheduler? = null

Scheduler that receives PagedList updates, and where PagedList.Callback calls are dispatched. Generally, this is the UI / main thread.
backpressureStrategy: BackpressureStrategy = BackpressureStrategy.LATEST

BackpressureStrategy for the Flowable to use.
See also
RxPagedListBuilder
toObservable

toFlowable

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toFlowable(
    pageSize: Int,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchScheduler: Scheduler? = null,
    notifyScheduler: Scheduler? = null,
    backpressureStrategy: BackpressureStrategy = BackpressureStrategy.LATEST
): Flowable<PagedList<Value>>

Constructs a Flowable<PagedList>, from this DataSource.Factory, convenience for RxPagedListBuilder.

The returned Flowable will already be subscribed on the fetchScheduler, and will perform all loading on that scheduler. It will already be observed on notifyScheduler, and will dispatch new PagedLists, as well as their updates to that scheduler.

Parameters
pageSize: Int

Page size.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / DataSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchScheduler: Scheduler? = null

Scheduler used to fetch from DataSources, generally a background thread pool for e.g. I/O or network loading.
notifyScheduler: Scheduler? = null

Scheduler that receives PagedList updates, and where PagedList.Callback calls are dispatched. Generally, this is the UI / main thread.
backpressureStrategy: BackpressureStrategy = BackpressureStrategy.LATEST

BackpressureStrategy for the Flowable to use.
See also
RxPagedListBuilder
toObservable

toObservable

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toObservable(
    config: PagedList.Config,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchScheduler: Scheduler? = null,
    notifyScheduler: Scheduler? = null
): Observable<PagedList<Value>>

Constructs a Observable<PagedList> from this DataSource.Factory, convenience for RxPagedListBuilder.

The returned Observable will already be subscribed on the fetchScheduler, and will perform all loading on that scheduler. It will already be observed on notifyScheduler, and will dispatch new PagedLists, as well as their updates to that scheduler.

Parameters
config: PagedList.Config

Paging configuration.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / DataSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchScheduler: Scheduler? = null

Scheduler used to fetch from DataSources, generally a background thread pool for e.g. I/O or network loading.
notifyScheduler: Scheduler? = null

Scheduler that receives PagedList updates, and where PagedList.Callback calls are dispatched. Generally, this is the UI / main thread.
See also
RxPagedListBuilder
toFlowable

toObservable

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toObservable(
    config: PagedList.Config,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchScheduler: Scheduler? = null,
    notifyScheduler: Scheduler? = null
): Observable<PagedList<Value>>

Constructs a Observable<PagedList> from this DataSource.Factory, convenience for RxPagedListBuilder.

The returned Observable will already be subscribed on the fetchScheduler, and will perform all loading on that scheduler. It will already be observed on notifyScheduler, and will dispatch new PagedLists, as well as their updates to that scheduler.

Parameters
config: PagedList.Config

Paging configuration.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / DataSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchScheduler: Scheduler? = null

Scheduler used to fetch from DataSources, generally a background thread pool for e.g. I/O or network loading.
notifyScheduler: Scheduler? = null

Scheduler that receives PagedList updates, and where PagedList.Callback calls are dispatched. Generally, this is the UI / main thread.
See also
RxPagedListBuilder
toFlowable

toObservable

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toObservable(
    pageSize: Int,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchScheduler: Scheduler? = null,
    notifyScheduler: Scheduler? = null
): Observable<PagedList<Value>>

Constructs a Observable<PagedList> from this DataSource.Factory, convenience for RxPagedListBuilder.

The returned Observable will already be subscribed on the fetchScheduler, and will perform all loading on that scheduler. It will already be observed on notifyScheduler, and will dispatch new PagedLists, as well as their updates to that scheduler.

Parameters
pageSize: Int

Size of pages to load.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / DataSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchScheduler: Scheduler? = null

Scheduler used to fetch from DataSources, generally a background thread pool for e.g. I/O or network loading.
notifyScheduler: Scheduler? = null

Scheduler that receives PagedList updates, and where PagedList.Callback calls are dispatched. Generally, this is the UI / main thread.
See also
RxPagedListBuilder
toFlowable

toObservable

android 
fun <Key : Any, Value : Any> DataSource.Factory<Key, Value>.toObservable(
    pageSize: Int,
    initialLoadKey: Key? = null,
    boundaryCallback: PagedList.BoundaryCallback<Value>? = null,
    fetchScheduler: Scheduler? = null,
    notifyScheduler: Scheduler? = null
): Observable<PagedList<Value>>

Constructs a Observable<PagedList> from this DataSource.Factory, convenience for RxPagedListBuilder.

The returned Observable will already be subscribed on the fetchScheduler, and will perform all loading on that scheduler. It will already be observed on notifyScheduler, and will dispatch new PagedLists, as well as their updates to that scheduler.

Parameters
pageSize: Int

Size of pages to load.
initialLoadKey: Key? = null

Initial load key passed to the first PagedList / DataSource.
boundaryCallback: PagedList.BoundaryCallback<Value>? = null

The boundary callback for listening to PagedList load state.
fetchScheduler: Scheduler? = null

Scheduler used to fetch from DataSources, generally a background thread pool for e.g. I/O or network loading.
notifyScheduler: Scheduler? = null

Scheduler that receives PagedList updates, and where PagedList.Callback calls are dispatched. Generally, this is the UI / main thread.
See also
RxPagedListBuilder
toFlowable